# Java Program to solve Towers of Hanoi puzzle using Recursion

One of the powerful example for solving a problem using recursion is Towers of Hanoi puzzle. This tutorial covers about what is Towers of Hanoi puzzle and how to solve the puzzle using recursion.

What is Tower of Hanoi puzzle? . We have three poles (or towers or rods), where the first pole has stack of different size disks. Let us label the first pole as ‘pole1’ , Second pole as ‘pole2’ and third pole as ‘pole3’

We have to move all the disks from the first pole (pole1) to the third pole (pole3) with the following conditions

1. At a time one disk can be moved

2. Big disk can not be placed on top of smaller disks

3. The second pole (pole2) is used as the temporary pole to hold disks

The above difficult problems can be easily solved by the technique Divide and conquer which divides the difficult problem into sub-problems recursively and finally the solution to all sub-problems is merged into a single solution of the difficult problem. Let us solve the above problem using recursion.

Let us assume that initially pole1 has n number of disks. disks are numbered 1 to n where disk 1 is smallest disk and disk n is the biggest disk. To move n disks from pole1 to pole3 , break the problems into sub problems as given below.

move n−1 disks from pole1 to pole2. // repeatedly called using recursion
move  1 disk (i.e. disk n)  from pole1 to pole3 // call move method
move n−1 disks from pole2 to pole3 // repeatedly called using recursion

The code to solve the problem using recursion is as follows.

```
package com.javaonline;

class HanoiTowers
{
public static void main(String args[]) {
HanoiTowers(4,"pole1" ,"pole3","pole2"); //totoal 3 disks ( disk 1 - smallest , disk 2 , disk 3 - biggest). pole2 is the temporary pole
}

private static void HanoiTowers( int n, String source ,String dest, String temp) // moving source                                                                                                       to destination using temporary
{
if (n == 1) move(n, source, dest );
else {
HanoiTowers( n-1, source,temp,dest ); //moves n-1 disks from pole1 to pole2 .
move( n, source, dest ); // moves disk number n from pole1 to pole3 , here n is the                                                                  top disk number in the source
HanoiTowers( n-1, temp , dest,source ); //moves n-1 disks from pole2 to pole3
}
}

private static void move (int diskNo, String source , String dest)
{
System.out.println("disk " + diskNo + " moves from top of " + source + " to top of " +dest );
}

}```

Output :

In the above program , instead of calling move method , you can directly call print statement. I have used move method for better understanding of the program.

Now let us calculate how many moves are required to move n disks from source to destination. The biggest disk is required the least number of moves (i.e. 1) and the smallest disk is required most number of moves. For example , if a pole have 4 disks (disk 1 , disk 2 , disk 3, disk 4) , then the disk 4 is moved one time only, disk 3 is moved 2 times , disk 2 is moved 4 times , disk 1 is moved 8 times. Total of 15 moves are required. So The number of moves required to solve a Tower of Hanoi puzzle is 2^n -1, where n is the number of disks

male enhancement that works fast male enhancement pills online india supplements for seminal volume best male enhancement 2020 r1 male enhancement reviews which penis pills work swiss navy male enhancement reviews where can i buy ed pills over the counter black male enhancement pills jenna jameson penis pills enzyte male enhancement bob ads male enhancement natural exercises male enhancement patches work how to make blood flow to your penis no pills pink pill v viantis male enhancement pills otc ed pills kroger alpha booster pills viagra pill pictures virility enhancement pills orange pill no markings france t253 male enhancement sex pills ashwaganda male enhancement supplements to make you more vascular where can i buy 1 viagra pill what is a dietary male enhancement realistic penis enlargement topicals glans enlargement orgazen gold 5800 male enhancement sex pills robust male enhancement

best diet for extreme weight loss gnc apple cider vinegar pills for weight loss egg white diet for weight loss drastic weight loss pills fda banned weight loss supplement list pescatarian weight loss diet best supplements for weight loss 2020 khloe kardashian weight loss diet keto diet friendly thanksgiving recipes low calorie diet for quick weight loss weekly diet plans to lose weight 5 day diet plan to lose weight does a high fibre diet help lose weight weight loss pills for children energy medicine for weight loss asian diet and weight loss is vitamin b12 pills good for weight loss diet pills to help with weight loss beachbody weight loss supplements best supplement for muscle growth and weight loss weight loss surgery diet without the surgery weight loss bean diet sletrokor weight loss pills side effects probiotics supplements weight loss otc weight loss pills for kids supplement pills to lose weight perfect indian diet chart for weight loss food detox diet for weight loss daylight diet weight loss keto dog diet recipes

cbd oil arthritis top 10 cbd where is cbd legal nj cbd laws cbd coupons codes canna blast cbd cbd suppository cbd green cbd oil sacramento cbd oil sublingual cbd oil for focus cbd heart benefits thc or cbd for sleep cbd oil trump co2 extracted cbd oil for sale cbd oil companies mg of cbd cbd oil for adhd child cbd kannaway miracle cbd gummy bears nixul cbd can you get a prescription for cbd altus cbd pills review cbd stricture icd 10 shingles and cbd oil cbd oil for animals active releaf cbd oil cbd group inc is cbd oil illegal in new york state kanna cbd oil 1000mg